The present invention relates to chromatography columns and in particular to a chromatography column system and method of packing a chromatography column.
Frequently it is desirable to separate out one or more useful components from a fluid mixture that contains other components which may not be useful or are less valuable. To accomplish this it is often necessary or desirable to fractionate such a fluid mixture to separate out the useful or desired components. This can be carried out by using liquid chromatography systems. Liquid chromatography may briefly be described as the fractionation of components of a mixture based on differences in the physical or chemical characteristics of the components. The various liquid chromatographic systems fractionate the components with a fractionation matrix. Some liquid chromatographic matrix systems fractionate the components of a mixture based upon such physical parameters as molecular weight. Still other liquid chromatographic systems will fractionate the components of a mixture based upon such chemical criteria as ionic charge, hydrophobicity, and the presence of certain chemical moieties such as antigenic determinants or lectin-binding sites on the components.
Chromatography systems of various sized are used in both laboratory analysis operations and for industrial scale production operations in which separation steps such as separating out a fraction from human blood or separating out impurities from a pharmaceutical can be carried out on a large scale in a batch process.
The development of chromatography columns has aimed at providing ease of operation and various additional benefits which have particular commercial importance. These include: (a) the ability to be sterilized by autoclaving; (b) improved sanitation by virtue of design features giving less carryover of product from one batch to the next; (c) the ability to resist solvents; (d) material conformity to food grade FDA regulations; (e) an improved pressure tolerance; (f) lower cost; and (g) the potential for full or partial automation.
Traditionally, a chromatography column must be disassembled to reslurry and remove chromatography media in order to repack the chromatography column with fresh chromatography media or with different chromatography media specific for an application. This procedure has several problems. First, the time required to perform this operation is substantial, especially with large industrial columns, and results in lost productivity in a commercial operation. Second, the constant assembly and disassembly of the chromatography column creates excessive wear on the components and leads to a reduced life of the chromatography system. Third, mechanical lifting equipment and significant floor and head space are required finally, each time a chromatography column is disassembled there are increased opportunities for unwanted contaminants to be introduced into the column, which can subsequently contaminate the fluid mixture and fraction of interest.
Another problem associated with some types of chromatography columns is the inability to clean the flow path used to introduce chromatography media into the chromatography column while maintaining a barrier between the cleaning solution and the packed chromatography media.
A known chromatography column is illustrated in FIG. 1 which employs two valves, one is located at the top of the column and the other spaced from it at the bottom. Each valve has three ports. Port 1 is for feeding slurry into the column during packing and for pumping liquid into the column for reslurrying during unpacking. Port 2 is for expelling xe2x80x9ccleanxe2x80x9d liquid pumped via port 1 to flush out the slurry line after packing, and for removal of reslurried gel during unpacking. Port 3 is the inlet and outlet for the mobile phase, and communicates directly with and only with the distribution cell.
The valves 11 are each as shown in more detail in FIG. 2 in which a pneumatically actuated valve sleeve can assume three different positions depending upon the mode of operation. In the bottom valve during packing, the valve sleeve is in the semi-retracted packing position, as shown in FIG. 2, which closes off port 2 from communication with the inside of the column. When in this position, slurry is pumped into the column via port 1 of the bottom valve, and air or excess liquid is removed via port 2 of the top valve. When the column is purged of air, the valve sleeve of the top valve is in the closed position (i.e. fully extended into the housing).
In the run position, the valve sleeves for both the top and bottom valves 11 are in the unactuated position, closing port 1 and port 2 of both valves from the inside of the column. When in this position, clean liquid can be pumped from port 1 to port 2 to remove any media (gel) left in the slurry line or to carry out a clean-in-place (xe2x80x9cCIP)xe2x80x9d cycle on these lines. The column is then run by pumping mobile phase through port 3 to (and from) the distribution cell.
There are three methods to reslurry a packed bed employing these valves. In the first method, the bottom valve is in the fill (valve sleeve partly retracted) position and the top valve is in the drain position where the valve sleeve of the top valve is fully retracted from the column housing. When the valve sleeve of the top valve is in this position, clean liquid can be pumped via port 1 through the nozzles at the end of the tube to reslurry the gel, which is then removed through port 2. In the second method, both the bottom and to valves are in the drain position (with the sleeves fully retracted). Clean liquid is pumped into the column via port 1 of either the top or bottom valve to reslurry the gel. Reslurried material passes out through the bottom of the column. In the third method, the top valve is in the fill (sleeve partly retracted) position and the bottom valve is in the drain (sleeve fully retracted) position. This enables slurrying of the top of a packed bed and the slurry passes out of the bottom valve. All three methods can be used in combination during a reslurry operation.
To drain or empty the column, both top and bottom valves are in the drain position and either pump is reversed to withdraw liquid from the column. Alternatively, a combination of pumps may be used to inject and drain the column simultaneously through port 2 on either valve. In addition, slurry may be recycled to the column to greatly reduce the quantity of clean liquid needed to flush the column.
The above described prior art valve has a rather complex construction to ensure the sleeve adopts the required operative positions with implications for reliability and manufacturing costs.
The chromatography column of PCT/GB97/02943 discloses a chromatography column which can provide the same functional capabilities of the above described prior art column, with a valve of reduced complexity, and so more economic to manufacture which can provide increased reliability and be operable to vent the volume in the event of accidental over-pressurization. This column is shown in FIGS. 3 and 4.
The valve has two operative positions, only, thereby allowing a reduction in the complexity of the valve. Because the central bore and passageway are always in fluid communication, should there be an accidental over-pressurization of the column during packing via the passageway in the longitudinal member, the media can enter the central bore thereby venting the column and relieving the overpressure. This is in contrast to the situation in which an over-pressurization occurs during packing with the above described prior art valve as the passageway and central bore are not in fluid communication during packing so no venting is possible if only one valve is present.
A known method of packing such columns is to prepare a slurry in which one or more solutes are transferred from a fluid to the surface of a solid phase where they are adsorbed include contacting of the component with the solid particles by the passage of flow through a packed chromatography bed and batch adsorption of the component or a product of a in-situ reaction onto the solid particles in a stirred tank and then gravity settling or other traditional column packing techniques to form a packed bed.
The present invention seeks to provide an improved chromatography column system and method of packing a chromatography column, which system and method are as claimed in the claims.
A method according to a first aspect of the present invention is a method of packing a chromatography column with a chromatography media from a slurry vessel in which a slurry containing the chromatography media is pumped into the chromatography column to pack the column and excess fluid from the chromatography column during packing is returned to the slurry vessel.
The media can be added to the vessel bit by bit until the column is fully packed so reducing the waste that can be associated with prior art packing methods where the initial quantity of media should be at least what is required for packing to ensure the vessel does not become exhausted of media before packing is completed.
A method according to a second aspect of the present invention comprises preparing a slurry including a chromatography media prior to packing a chromatographic column with the chromatography media including adding the components of the slurry to a slurry vessel and then circulating the slurry from the slurry vessel and returning them to the slurry vessel.
The chromatography media and the liquid components including a target component are introduced into the vessel and the mixture circulated from and back to the vessel to prepare the slurry. This provides a self contained batch adsorption operation where the chromatography media is contacted by components in the fluid and adsorption occurs. The slurry is then pumped in the chromatography column to effect packing of the column. Subsequent recovery of these components can then be effected by a chosen chromatographic procedure.